Calculating device



Aug. 19, 1941.

H. w. BACKMAN ETAL 2,252,749 CALCULATING DEVICE Filed March 21, 1939 3 Sheets-Sheet l PRESSURE 8 E PRESSURE STORY OF TION INCREASE 5 LBS FOR ELE Aug. 19, 1941. H. w. BACKMAN ETAL 2,252,749

CALCULATING DEVICE Filed March 21, 1939 I 3 Sheets-Sheet 2 I I I I I l a I I I I I I I I I I fzwezaiva s aw; w. Wm M a. g

9, 1941. H. w. BACKMAN ET AL 2,252,749

CALCULATING DEVICE- Filed March 21, 1939 3 Sheets-Sheet 3 Patented Aug. 19, 1941 CALCULATING DEVICE Henry W. Backman and Luther A. Powers, Jr. Waltham, Mass.

Application March 21, 1939, Serial No. 263,170

3 Claims.

This invention relates to calculating devices and consists in particular of a device for calculating hydraulic pressures, being particularly useful in conjunction with fire-fighting apparatus. In fighting fires, various types of hose nozzles are used in combination with different lengths of hose. Usually a pump is mounted on a fire truck and arranged to take water from a hydrant or other source and deliver it at increased pressure through the fire hose to the nozzle. Heretofore the operator of the pump has had to depend upon his skill and judgment for regulating the action of the pump to supply sufficient water to cover the fire and yet keep the pressure at the nozzle low enough so that the hose can be managed without too much difficulty by the firemen.

The most important object of our invention is to provide a simple calculating device adapted to be mounted on a fire pump and by means of which the pump attendant or engineer can determined quickly and accurately the proper pump pressure to maintain under any given set of conditions.

The calculating device of our invention may be so constructed that by manipulating two knobs the pump operator can determine the proper pump pressure for any given combination of nozzle diameter, desired nozzle pressure, and length of hose. While the result can be figured on paper if time is available by using various formulae involving coefiicients of hose friction, nozzle data, etc., the calculations involved in solving the formulae are beyond the comprehension and skill of the ordinary pump operator. The device of our invention indicates the solution of the problem plainly as soon as the known data is registered in it.

These and other objects and features of our invention will be more readily understood and appreciated from the following detailed descrip: tion of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawings, in which Fig. 1 is a plan view of the device,

Fig. 2 is a view in cross section along the line 22 of Fig.1,

Fig. 3 is a plan view of the device with the top plate removed,

Fig. 4 is a plan view of the base of the device with all the plates removed,

Fig. 5 is a bottom plan view of the lowermost plate,

Fig. 6 is a view in cross section along the line 6-6 of Fig. 1, and

' side thereof.

Fig. 7 is a view in cross section on the line 'l---'! of Fig. 1.

In the device shown in the drawings a dished base ID of metal or other suitable material is formed as shown in Fig. 2, and provided with a sheet casing H. Bolted inside the base II] is a metal socket l2 which receives an upright spindle |4secured in place by a set screw 15. The upper part of the socket I2 forms a bearing surface for a sleeve I8 and a hub 20 held fast to the sleeve l8 by a set screw 2|. The hub 20 is integral with a segmental gear 22 as shown in Fig. 5. At

either end of the segment small metal rods 24 are welded and extend radially beyond the teeth of the gear to form stops. Fixed to the end of a curved arm 26 is a freely turning roller 28 which engages the teeth of the segmental gear 22. At the other end of the arm 26 is a hub 30 as shown in Fig. 4 which pivots about a spindle 32 threaded into the base ID at one A helical spring 34 is connected to the socket l2 and to the arm 26 so that the roller 28 is yieldingly forced against the segmental gear 22. Above the segmental gear 22 and freely turning about the sleeve l8 and the spindle I4 is a spur gear 36 having a hub 31 which is shaped to space the gears 22 and 36. A freely turning roller 38 is secured to an angular shaft '39 held in a fitting 40 by a set screw 4|; the fitting 40 is welded to one element of a hinge 42, the other element of which is secured to the base In. A spring 43 is connected to the shaft 39 below the roller 38 and to the socket 12 so that the roller 38 is held in yielding engagement with the teeth of the spur gear 36. The upper face of the spur gear 35 is secured to a thin metal plate 44 of circular form which in turn is secured in face to face contact with a larger circular disk 45. As shown in Fig. 3, the disk 45 is provided on its upper face with radially arranged numbers which represent the various pressures at which the'pump could be run, as will be fully explained below. For convenience we prefer to designate this plate 45 as the pump pressure disk.

A metal masking plate 46 smaller in diameter than the disk 45 is eccentrically secured to the sleeve I8 to save material and is provided with a series of spirally arranged rectangular holes or sight openings 41 through which the figures on the pump pressure plate 45 may be read. superposed above the plates 45 and 46 is a top plate 48 shown in Fig. 1 secured in place by a screw threaded into the spindle l4. Fire hose data is almost universally compiled as the basis of 100 foot lengths and in conjunction with one of three standard nozzles having diameters of 1", 1 and 1 Radially arranged on the margin of the top plate 48 are thirty number combinations representing ten different hose lengths in combination with the three standard nozzle diameters. That is to say, each combination of hose length and nozzle diameter has a specific location indicated on the top plate 48 as will be apparent from an inspection of Fig. 1. The top plate 48 is provided with a curved slot or sight opening 49 below which appear figures indicating nozzle pressure and ranging from 25 lbs to 60 lbs in 5 lbs. stages. An upright rod or pointer 50 is secured to the face of the masking plate 46 and extends up through the curved slot 49 in the top plate 48.

It will be understood that the masking plate is fast to the segmental gear 22 through the sleeve l8 and that as the rod 50 is moved from one nozzle pressure to another the roller 28 acting on the segmental gear 22 will cause the rod to stop in predetermined locations, that is to say, exactly opposite one of the indicated nozzle pressures. In other words, the rod 50 and the gear 22 are carefully assembled so that when the roller 28 stops the movement of the rod 50 by reaching a point between two teeth, the rod 50 will then be exactly opposite one of the nozzle pressure figures. The top plate 48 is also provided with a radial sight opening or slot 5| about which we prefer to set the words Engine pressure as shown in Fig. 1. Through the slot 5| may be seen the masking plate 46, which may conveniently be colored black. One of the rectangular holes 41 in the masking plate 46 will be always seen through the slot 51 in the top plate 48, and through the hole 41 may be observed one of the figures from the pump pressure disk 45. A knob 53 and a pointer 54 are secured to the plate 44 and arranged so that the pointer 54 is directed toward the marginal figures on the top plate 45. The pointer 54 and the teeth of the spur gear 36 are carefully arranged so that the roller 38 will stop the pointer 54 only when at an exactly opposite one of the marginal figures on the top plate 48. Of course, it is to be understood that the rollers 28 and 38 do not positively stop their respective gears against further movement but act only as detents to make it impossible for the rod 50 or the pointer 54 to stop at a location other than exactly opposite one of the figures at which they may be set.

In operating the device it is only necessary for the pump operator or engineer to ascertain the length of hose being used. He will of course know the type of nozzle being used by his com pany, and the nozzle pressure desired is generally a standing requirement of the chief or other oflicial in the fire department, so that in all events, the pump operator will know beforehand the nozzle diameter and the desired nozzle pressure. When the pump operator has ascertained the length of hose being used, he then moves the knob 53 around the periphery of the plate 48 until the pointer 54 is opposite the figure indicating the particular length of hose and nozzle diameter being used. The rod 50 is then moved opposite the nozzle pressure desired. As shown in Fig. 1, 200 feet of hose and a 1" nozzle are being used, and the nozzle pressure desired is 55 lbs. By looking through the slot 5| in the plate 48 the operator will find that the masking plate 46 has uncovered the number 80 on the pump pressure plate 48. The pump operator will then know that if he regulates his engine so that the water pressure indicator at the pump reads lbs, he is supplying sufiicient Water to the nozzle and is not overloading the hose so that it is diificult to direct.

A formula for finding approximate engine pressures for use with standard 2 fire hose is:

E. P.=N. P. (l.1+(K L)),where N. P: nozzle pressure; K is a constant varying with the nozzle diameter; and L is the number of 50 foot lengths of fire hose between the pump and the nozzle. For nozzle diameters of 1", 1 /8", and 1% the values of K are .105, .167, and .248 respectively. By using the above formula the pump or engine pressure can be roughly figured, but it is obvious that the average pump operator cannot solve the formula in his head, especially with all the excitement of a fire going on about him. It is apparent that the figures on the plates could be changed for varying conditions. The figures could be calculated to read for hose diameters other than the standard 2 /2", or for siamese hose, different nozzle diameters, etc.

Although the advantages resulting from the use of our invention are obvious, it will be well to point out that it is an important aid in sliort ening the time within which an effective stream of water may be efficiently directed on a fire. It is also advantageous in that even an unskilled pump operator can perform his task efficiently in spite of the fact that the nozzle may be out of sight, thus, eliminating the present practice of sending a fireman back to the pump to call for more or less pressure, and resulting in a saving of man power. It is also important to note that the use of our invention results in lengtl1ening the life of the fire hose, since the hose is never overloaded or given a greater burden than it is necessary for it to carry. These considerations also apply to the pump. The use of our invention results in lessening the hazard to hosemen when engaged in directing a stream from an icy roof or other precarious position, since the pressure in the hose is always kept within safe limits.

Pumping engines are tested periodically and our invention is very useful in this work because it cuts down the time consumed by laboriously calculating from formulas. In testing the pump a pressure gauge is placed across the end of a nozzle and the pump is operated to pump water through a length of hose and the nozzle. By determining the pressure at the pump and at the nozzle and taking into account the length of hose being used, the efficiency of the pump can be checked. With our invention this may be accomplished by setting the pointer 54 opposite the proper number indicating the length of hose and nozzle diameter and reading the gauge on the nozzle. Then the actual nozzle pressure given by the gauge is applied by moving the knob 50 to the proper location and checking to see whether or not the pressure gauge at the pump gives a reading similar to that shown in the engine pressure slot 5| of our device. That is to say if 200 feet of hose and a l nozzle are being used and the nozzle pressure is found to be 55 pounds (using the figures as shown in Fig. 1) the pressure shown on the gauge at the pump should be 80 lbs. If the pressure at the pump is higher than 80 lbs., it becomes apparent that the pump is not operating efiiciently.

Although we have described our invention as applied to fire-fighting equipment, we definitely contemplate other uses for it. For example, oil is often pumped from a shore refinery or storage tank through a long hose to an anchored ship. With suitable alterations in the figures on the various plates, to take care of the much greater lengths of hose involved, our invention may be employed to determine the proper regulation of the oil pumps. Inasmuch as special hose has to be used for this purpose it is very important that its life be prolonged, and by using the device of our invention the oil can be transferred as efficiently as possible without endangering the hose. It is also apparent that our invention can be profitably used in conjunction with hydraulic mining. The recitation of specific uses of our invention is not comprehensive but illustrative and it will be apparent that the invention can be used in numerous ways by varying the indicia on the plates without departing from the spirit of the invention.

Having thus described our invention what we claim as new and desire to secure by Letters Patent of the United States is,

1. A device for solving the hydraulic formula E. P. :N. P. [1.1+(K L)l for different values of N. P., K,. and L., which comprises three superposed disks of which the top disk is fixed, pro vided with two slots and bears on its face a range of combined K L values disposed along the margin and a range of N P values disposed radially and spaced from the margin, the second disk being blank except for a series of spirally arranged apertures, a pointer fast to said second disk and working in one slot in the top disk adjacent the range of NP values, movement of said pointer causing said second disk to rotate relatively to said top disk, the third disk bearing EP values on its upper face, and a knob fast to said third disk and working about the circumference of the top disk adjacent the combined K and L values, whereby said knob may be set opposite a given K L value, movement of the knob causing the third disk to rotate and set up a range of EP values beneath the second slot in the top disk and whereby the pointer may be set to a given N-P value, whereupon the second plate is moved to mask all the values set up beneath the second slot in the top disk except the one which represents the E-P value when N. R, K, and L are at the values indicated by the pointer and the knob.

2. For use with a driven pump for delivery of fluid through a conduit or hose of known length and diameter to a remote nozzle of known diameter, a device for rapidly predicting the pressure adjustment for said pump required to maintain a predetermined pressure at said nozzle while in use, said device comprising a relatively fixed upper plate, a series of combined hose length and nozzle diameter notations marginally positioned on said plate, a first opening and a sight opening in said plate, a series of nozzle pressure notations positioned adjacent one of said opena relatively movable under plate, marginal pointing means fixed to said under plate, a series of pump pressure notations on said under plate, a relatively movable masking plate between said upper plate and said under plate, pointing means fixed to said masking plate and positioned to coact with said nozzle pressure notations and said adjacent opening. and sight opening means positioned in said masking plate, whereby the movement of said marginal pointing means to one of said hose length notations together with the movement of said other pointing means to one of said nozzle pressure notations will automatically expose through the other of said openings the pump pressure notation for the adjustment of said pump appropriate for said hose length notation and said nozzle pressure notation.

3. A device for solving the hydraulic formula E. P.=N. P. [1.1+(KXL) which comprises an upper disk fixed on a spindle, combined K and L values disposed around the margin of the upper disk, N. P. data disposed along an arcuate slot in the upper an intermediate masking plate rotatably mounted on the spindle beneath the upper disk and provided with a series of spirally arranged perforations, a pointer secured to the upper surface of the masking plate and projecting through the said arcuate slot, at lower disk rotatably carried on the spindle beneath the masking plate and bearing E. P. values arranged radially thereon, and a second pointer fast to said lower disk and directed toward the K and L values on the upper disk.

HENRY W. BACKMAN. LUTHER A. POWERS, JR. 

